- I learned Korean in Busan (where there is a very well known dialect), so I can only speak from my experience. Where I am from, ~ㅆ나 is used to denote a yes or no question. "Did you eat?" -> 먹었나? "Did you go?" -> 갔나? "Is it fun?" -> 재미있나? - For your second question, as Ghye answered, it means "try" or "have a go". When said as a declarative, it means to try to do something "먹어봤나?" "Did you try it/try tasting it/try eating it?". "해볼게요" "I am going to try to do it". It can also be used as an imperative when using it to someone else. "해봐!" "Try it!" To soften a command, you can even use it twice "해봐봐" -> "Lit: Try and try it, "try doing it". - As for the diphthong question, I think it partly has to do with the fact that many diphthongs are softer and more languid in Korean than perhaps English, which leads to what you are talking about. Once again, where I live the accent was a bit different, but everyone I knew pronounced it as 바 and not 봐. - That form is used in grammar but it is also known as the written form. Words with a 받침 add 는다 in present tense. 먹는다, 읽는다, and so on. Words that end in ㄹ follow the irregular conjugation rules, and therefore the ㄹ is replaced by a ㄴ -> 살다 -> 산다. Keep in mind, this rule for written form is only followed for verbs, not for adjectives. So 멀다 (to be far) would stay as 멀다.

# it's possible both in past and present tense as you said. # 봐 is correct, not 바. You can suggest something with this expression. e.g. 해봐means "have a go". We sometimes says 봐 similar to 바 for making it easy to pronounce. But originally different pronounciation. # all correct except for 읽는다, 먹는다